The present invention relates to a hemagglutinin, that is, lectins extracted from plant seeds, especially the plants of the class Dicotyledoneae, and the antiretroviral drugs containing such lectins as active ingredient.
In recent years new types of viral diseases such as B type hepatitis, adult T cell leukemia and AIDS (acquired immunodeficiency syndrome) have been attracted. Human being has combatted the viral diseases by means of vaccination and succeeded in eradicating such diseases as smallpox, yellow fever and polio. However, vaccination alone is not enough to cope with the diseases involving the problem of persistent infection or cryptogenic infection such as AIDS, and thus the development of an antiviral drug which is safe and highly efficacious has been expected.
The present inventors had previously proposed polysaccharides extracted from the fungi of Basidiomycetes, showing an anticancer effect. For instance, in British Patent No. 1,331,513 is disclosed polysaccharides obtained from a liquid extract of a mycelium of a fungus species of Basidiomycetes or from a cultured broth of said species, said polysaccharides being free or substantially free of impurities originally present in said liquid extract or in said cultured broth, and being characterized by being a water-soluble amorphous solid which is non-hydroscopic and non-dialyzable; gives a positive result when tested for the presence of glucose after hydrolysis with 1N sulphuric acid; gives negative results when subjected to the ferric chloride reaction for determining the presence of phenols and to the Fehling reaction for determining the presence of reducing sugars; gives positive results when subjected to the anisaldehydesulphuric acid reaction, the Molish reaction with .alpha.-naphthol, the anthrone-sulphuric acid reaction, the tryptophane-sulphuric acid reaction, the chromotropic acid-sulphuric acid reaction, the aniline-hydrochloric acid reaction, the resorcinol-hydrochloric acid reaction, the carbazole-cysteine-sulphuric acid reaction, the Tollens reaction and the thioglycol-sulphuric acid reaction; shows only one spot at the anode side when subjected to electrophoresis in a 0.05 mol. sodium borate solution for 90 minutes using a cellulose acetate membrane at 20-25 V/cm; and shows no antimicrobial action to bacteria, fungi and yeasts such as Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Aspergillus niger and Candida albicans.
As a result of the present inventors' studies for providing a medicinal substance which is safe and has an excellent antiretroviral activity, it has been found that lectins obtained from the plants of the class Dicotyledoneae have a function to inhibit the activity of reverse transcriptase as well as an inhibiting activity against adsorption of human immunodeficiency viruses (HIV) on human lymphocytes. The present invention has been attained on the basis of such finding.